During the lifetime of a patient, it may be necessary to perform a joint replacement procedure on the patient as a result of, for example, disease or trauma. The joint replacement procedure may involve the use of a prosthesis which is implanted into one or more of the patient's bones. In the case of an ankle replacement procedure, a tibial component is implanted into the patient's tibia, and a talar component is implanted into a patient's talus. A polymer bearing insert is positioned between the tibial component and the talar component. The articular surface of the talar component bears against the articular surface of the bearing insert.
Depending on the condition of the patient's soft tissue, either an unconstrained ankle prostheses or a semi-constrained ankle prosthesis may be implanted. For example, if the patient's ankle ligaments are relatively intact, an unconstrained ankle prosthesis may be used. An unconstrained ankle prostheses has two articulating interfaces thereby creating desirable degrees of freedom. One articulating interface is between the tibial component and the bearing insert, with the other being between the bearing insert and the talar component. In the absence of sufficient soft tissue, a semi-constrained ankle prosthesis is used. Such an implant includes only one articulating interface—the interface between the bearing insert and the talar component. Unlike unconstrained implants, the polymer bearing insert is locked in position relative to the tibia component in a semi-constrained ankle prosthesis.